I have always been into everything...as my handle says on my blogs, I am a "Jack of all trades" and - I freely admit - a master of none. But I am constantly surprised at how much my fellow Telecomms techies DON'T know about electronics - which is after all what drives all the gear that we use.

Recently my company gave us all a raise in pay (yes it does happen!) but we were required to have a diploma level qualification to get the new pay scale. If we didn't have one (and mine were so old and from a galaxy so far, far away that they didn't count :-) the company paid for us to get one. This was done mostly via RPL - Recognition of Prior Learning - we had to write up jobs we had done that applied to the competencies we needed to get the qualification. It was an awakening for me - almost no technical stuff at all - more procedural rubbish on dealing with jobs in order of priority, obseving health and safety regulations, etc.

So I guess we all have our areas of expertise. I'm just so glad I came form an era where you had to know about the guts of the equipment and actually pulled it apart and fixed it instead of just swapping it out and sending the old one off for repair....

@david But I am constantly surprised at how much my fellow Telecomms techies DON'T know about electronics

Just a few days ago a lead tech came to me with a problem - help identify a device in a SOT143 package. He had already searched out some potential transistor candidates. Then emailed me a photo of the PCB etch.

Two of the 4 pins connected to the ground plane, one pin was capacitor coupled to an IC, the forth pin went to a mini coaxial cable connetor. There were four of these devices in all, four 50ohm coax cables connected the mini coax connectors to an OC48 (2488.32 Mb/s) optical receiver; two for differential data, two for differential clock, both ends AC coupled through a capacitor.

No bias-TEE anywhere. So why was he looking into transistor data sheets to try to find a match to the obscure code printed on the package when the circuit itself indicated this was a passive device, probably a R/C/L filter network?

@zeeglen: So why was he looking into transistor data sheets to try to find a match to the obscure code printed on the package when the circuit itself indicated this was a passive device, probably a R/C/L filter network?

@David: I'm just so glad I came form an era where you had to know about the guts of the equipment and actually pulled it apart and fixed it instead of just swapping it out and sending the old one off for repair....

I agree -- I'd go further -- I'm glad I came from the era when microprocessors were just coming online and memory was so small and expensive -- so you had to learn to create really efficient code that had th esmallest possible memory footprint and used the fewest number of clock cycles -- it gave you a real appreciation for what was going on "under the hood"...

... and you tell the young engineers today and they don;t believe you (mutter mutter mutter mutter...)

"In the high and far-off times", students learned to program with punched cards and paper listings, and if a student couldn't get a program to work he or she brought the listing to a "consultant" -- generally a near-mininum-wage CS student -- for help. My favorite story is that one day a student's program didn't produce any output at all. The consultant looked at the code, which was a total mess, but he couldn't figure out why it produced nothing instead of a bunch of error messages. Finally he saw that the student had commented out the entire program, which is why it didn't produce anything. When he pointed this out, the hapless student said: "But that's the only way I could get it to compile!"

I first off want to say hello to the community of EE Times! Even after being a member of the site for a while now, this is first time I have ever decided to leave a comment! But, first time for everything, right?

"This friend is a particularly bright guy with an MSEE, but he left engineering and went to "the Dark Side" (project management) about 30 years ago."

"How about someone being ignorant of something you would absolutely have assumed that person knew?"

Not going to lie, this one of my biggest fears once I retire as a student. This is also part of the reason why I decided to continue to my life on the "light side" as graduate student. I understand the importance, but it seems as though going into management is pretty lousy if it means potentially forgetting a lot of the technical (and more interesting) concepts, which even includes Ohm's Law for some people. Once, my dad's friend who used to work for TI asked me for assistance with an embedded project using a MCU. From working with me, he realized how lousy his C programming became since going into management. That's SUPER scary, I think. At this point in my life, I can hardly imagine not programming for more than a day, let alone long enough to forget anything.

"How about you? Have there been any occasions when you discovered that you'd forgotten some fundamental concept?"

As graduate student, I think I may have an advantage here, especially since I often have to review a lot basic concepts in preparation for more advance topics. Still, I remember the professor I had for Introduction to Machine Learning being fairly surprised at me (and the most of the class, if I may add) for stumbling with basic stastical and probability concepts (e.g. correlation, covariance, expectation, etc.).

@betajet: Your story about the student's commented code made my night, by the way.

Even after being a member of the site for a while now, this is first time I have ever decided to leave a comment!

Welcome! I hope you become an active particpant. I can only speak for myself, but I really appreciate it when someone actually responds to something I have said. I find it quite disheartening when I put several hours into a blog and it seems to fall on deaf ears.

Thanks for adding to the converstation. And to everyone else who only reads these blogs, please add to the vibrancy of the forums.

@antedeluvian: I find it quite disheartening when I put several hours into a blog and it seems to fall on deaf ears.

I knwo just what you mean -- sometimes I slog away at a column ... and no one says anything ... I'd like to think it was because they were left speechless by my brilliance, but I fear thsi is not the case LOL

On the other hand, when I post a blog like my recent Thanks, Dad! that gets a bunch of comments, then I bounce aroudn with a great big sloppy grin on my face :-)

@AndrewAPTemple: I first off want to say hello to the community of EE Times! Even after being a member of the site for a while now, this is first time I have ever decided to leave a comment!

Hello there -- welcome aboard :-) Hopefully we'll be seeing a lot more of you (comment-wise).

I make a lot of jokes about management and managers, but they do provide a necessary function (being the butt of my jokes, for example :-)

You cannot help but forget things -- especially things you don't use on a daily basis -- one of the best ways to stay on top of things (I think) is to have hobby projects that are outside of your usual work activities, because when you have a task to do you have to learn how to do it, and as long as you are learning stuff you seem to be better able to remember other stuff.

You cannot help but forget things -- especially things you don't use on a daily basis -- one of the best ways to stay on top of things (I think) is to have hobby projects that are outside of your usual work activities, because when you have a task to do you have to learn how to do it, and as long as you are learning stuff you seem to be better able to remember other stuff.

I'll keep those words in mind, especially when I finally I got into this professional, managerial world I keep hearing about.

And, I look forward to more interaction with the community (as opposed to only reading the articles), and the jokes!

@AndrewAPTemple: And, I look forward to more interaction with the community (as opposed to only reading the articles), and the jokes!

I lot of us have formed lasting friendships via EETimes and its sister sites -- some of us even manage to meet up at conferences. Maybe you will be able to attend some of these conferences after you've finished being a student. Where abouts are you based?

It's funny to see someone make simple assumptions that are probably wrong.

With the simple circuit and two "diodes" in series opposition one might conclude that only leakage current would flow for either polarity of input. But simple dismissal of the circuit may not be quite right.

Most LED's have extremely low reverse voltage capability. Most around 5-6V, or if they are more advanced, they have a parallel bulk protection diode in place and have a reverse voltage rating of only .8-1.2V.

In either case and with this circuit it's highly likely that current will flow for the AC half cycle shown.

In the case of Vr breakdown it might be 6V or so....add the protection diode Vf and you'd see something of the order of 7V across the diodes and about 9V across the resistor (about 17v peak from the AC 12v input). Current will flow (9/R) and it's unlikley to damage the LED (and of course you won't get any black light out of it....now that was a giggle)

There is no doubt that the circuit is non-ideal, but explaining that you must consider both polarities of input and the characteristics of the LED might have been better than dismissal.

Ah, the magic smoke ... how often I recall applying power to a prototype board and seeing a flash and basking in the acrid smell of magic smoke (and once it's escaped from a component, it's a bugger to get back in :-)

How about you? Have there been any occasions when you discovered that you'd forgotten some fundamental concept?
A more complete subject for this post would be " Things everyone should know, but, no one ever told me, and, it was too late when I realised."
1. Turn TRVs (Thermostatic radiator valves)up to max during the summer, when the central heating is off. This initially counter-intuitive idea is obvious when you think about it. During the summer the temperature in the room gets much higher than it does when you initially turn the valves to minimum in the spring. At the spring temperatures the valve is already trying to turn the flow off completely; in the heat of the summer the valve tries even harder to turn the flow off, resulting in a jammed or broken valve.
2. When hanging a door get a set of shorter and thinner screws than the ones you eventually intend to use. if you're a complete amateur like me you'll end up putting those screws in and out lots of times before you get everything right. Using smaller screws initially is a lot easier on your wrist, and does far less damage to the wood.

I have been faced many times with a few of issues for which I appear to be the only drummer. I've seen then sink projects, indirectly cause the loss of incalculable wealth, and I've even lost jobs, either because I was not "convincing enough" or "too insistent." I'm sure lots of other folks have encountered these too, but it's all the more frustrating as I KNOW they were part of the curriculum!

Number one is Nyquist. If you don't give him his due, his hoary ghost will invariably bite you in the butt. So many times I see data acquisition systems with no provision for an anti-aliasing filter, and often, those same systems are the targets of earnest but expensive and ineffectual "improvement." No, going to a 16-bit converter or a 1MHz rate won't help if you have broadband noise out into several MHz. A cheap capacitor is often all you need. Yes, it will attenuate high-frequencies, and slow the edges, but that is what it is SUPPOSED to do. A DAQ system is not an oscilloscope. And don't say to me "well, then, why doesn't a SCOPE need an input filter?"

Number two is dynamic range: a 12-bit converter with a +/-10V range should be preceded by an amplifier (or be switched to a diffferent gain) if you expect to measure a 1mV signal with any precision!

Watts are not linear. You can't filter (average) the I-signal and the V-signal and THEN multiply them! Here is a "quiz" I give to candidates, and sometimes to interviewers:

There's no trick, no esoteric knowledge, no calculations necessary, but 80% of engineers make the same mistake, that is, unless i "turn on" the two "hidden" questions.

Number five: expensive wire is only worth it if you actually USE the shield. Shields aren't magic, and attention to grounding goes a long way in improving measurements!

Just because two connectors feel like they hang-togeter is not sufficient to conclude that they are the appropriate combination to use. Manufacturers list compatibilities in their datasheets for a reason!

Protect your inputs! Just because the input impedance is listed as high (CMOS) doesn't mean you can neglect the case where the device is unpowered but connected to something that IS; "nobody would EVER unplug the tester while the DUT is still ON" is a cop-out.

Nice quizz, I will probably use it (with your permission) to demonstrate my customer why he should synchronize his software to measure U and I from a traction battery to evaluate the energy coming in and out of the battery for a State of Charge calculation.

I use this not only when talking about the basic concept of wattage not being a linear function, but also to illustrate the importance of doing sampling correctly, particularly the need for (as close to as possible) simultaneous sampling. Also, why a switching regulator is more efficient than a linear one, and why "peaky" current draw from a battery with internal R loses efficiency (sometimes, an LDO actually gives longer life in e.g. memory hold-up).

I can send you the original visio, but it's pretty effective when just sketched-out.

Surprising how many engineers don't get the PWM = linear variation of power concept.

One engineer I knew, that did understand the PWM concept, and then finely tuned his heater control loop, failed to appreciate the effect of "24v" supply voltage on a vehicle that could vary from 20v up to 29v (that's a power variation of 2.1 to 1).

Same guy failed to understand the concept of bouyancy, so putting the aforesaid heaters in top of the cabinet, and putting fans in the bottom with a chilling coil, assumed the air would circulate up one side and down the other. OK, With a small amount of heat , yes, the air did circulate, but put in a lot of heat , and you are left with a puddle of cold air at the bottom, and very bouyant hot air at the top, and the fan would not be strong enough to offset the bouyancy. Of course it's all in a feedback loop and basically latches up.

PS also agree on your other points, Why do some people (usually PhD's) use a high speed 16bit ADC with no anti-alias filter to measure something that could be done with 12bits a few times per second?

"Why do some people (usually PhD's) use a high speed 16bit ADC with no anti-alias filter to measure something that could be done with 12bits a few times per second?"

I feel for you, mate. I have MORE THAN ONCE been told "why would we need a filter? We're only sampling at once per second" Once, when the data turned-out bogus, the response was to discard all "out of range" values (leaving sparse data, and completely disguising a serious problem that later cost us >>£1E7). On THIS project, the decreed plan is to go to 16-bit, 200kS/s to solve the noise problem. The thought is that bigger spending gives better results, no? :-(

Incidentally, I've been in this game a long time, and the (a) correct way to do this stuff seems obvious to me, but maybe it isn't to everyone, so just let me describe a good default way to go when doing data acquisition:

Sample as fast as possible. If the achievable sample rate varies because of variable number of channels, use the lowest fs you are stuck with.

Use a correct anti-aliasing filter, that gives adequate attenuation at fNY (=fs/2) for your application. Its corner frequency must be lower than fNY; with a single-pole attenuation curve and high number of A/D bits, it must be surprizingly much lower. (If you want high (16-bit) accuracy, you have to trade-off frequency or filter complexity.) This is why you want fs as high as possible. Another reason is so you don't have to mess-around with this analog design once you have it working.

In the digital realm, perform any necessary calculations (offset cal, product [to get I*V=>W]), and then digitally filter the data on-the-fly down far enough that you can then decimate it to the needed final sample rate. This is done in every ΔΣ converter and is not weird or hard. With easy-to-deploy library "decimation" or "dual-rate" filters, the computations are very very efficient. "Averaging" is a kind of naïve filtering, but not as good as a proper Bessel, Butterworth Cauer, etc. design.

Of course there are lots of optimizations and compromises to be considered, but I think this is good as a basic approach, and I can cite a mountain of white-papers, appnotes, manuals and textbooks for further reference.

If you are stuck with a stream of bad data, there are only so many things to do. Heavy filtering, and relying on the gods of Noncorrelated Noise and the Law of Large Numbers are about it.

One guy I knew, who knew enough simple math for this, once got a 110V soldering iron in a set of tools from the USA, but he was in a 220V location. He figured that all he had to do was put a diode in series with the iron element and he'd be OK. The soldering iron burned out and he could not figure out why. I made him do the calculations, working out the resistance of the iron from the power at the rated 110v, then the power at 220v. Then halve that with a diode, and it's still twice as much as you should have. You could almost see the light bulb going on over his head :-)

Over my 30 + yrs career I could write a book of these ' lack of basic knowledge ' stories It is incredible how the more education engineers obtain the more they totally loose they basic EE knowledge ( if they ever had any ? ). I find it beyond comprehension that a PhD candidate can get a PhD degree and never once really do any real hands on electronics design.

I have a good friend who is a prof at a well know military school, who related such a story to me. Another EE professor who taught power systems engineering ( he has a MSEE in power systems ) was watching my friend prototype a circuit design. He ask my fiend which parts were the capacitors and which were the resistors ???

Gee I would not like to challenge him with a question as to what a drive motor looks like ??

When I graduated it was the era of 8008/8080. ADCs were pricey and every design (except maybe military) used a mux ahead of the ADC. I once spoke to a guy who graduated with me and so should have followed nominally the same growth path. He was designing an autoclave (sterilise medical instruments) and used about 6 individual ADCs that chnaged slowly, because he hadn't followed the technical journals and app notes.

Today things have changed, not completely, but it is now far more common to see multiple ADCs in a system. You can even get multiple ADCs inside a micro.

I don't often get involved in these basics things as much as I should, but sometimes I feel compelled to give a hint or two...

For computing power on a given circuit, it helps to think of locating all the forcing functions that produce a voltage or current, and then identify the loads of interest. If you have a voltage source, calculate the RMS voltage (which is defined to be the integrated voltage for POWER purposes). See the integral below, which applies for calculating the RMS value for one periodic piece of a waveform. In this case, T1 and T2 are the start and stop times of one period of the switch being on and off. To evaluate, break the integral into 2 pieces, one for the time of the switch being on, and then one for the time of the switch being off (T1 to Y for the first where the switch is on, then Y to T2 for the 2nd where the switch is off).

By the way, perhaps the reversed diode in the AC circuit for the LED was actually a zener!

Then, the circuit is exactly correct, given that he computes the zener voltage correctly and the resistor correctly. He also has to account for the fact that only 1/2 cycle will flow of the AC waveform, when he computes the power consumption. For the power computation, see my post in this topic for a hint about how to get the right answer! [For the 2v & 1ohm,